The present invention relates to novel brightener-leveler compositions useful in nickel electroplating and to a process for electroplating bright and level nickel surfaces onto metal substrates. It is already well known to use brightening agents in the acid plating baths to promote the formation of a bright nickel surface on articles to be plated. A variety of such brighteners are in commercial use and commonly include mixtures of acetylenic alcohols, and organic sulpho-oxygenated compounds, such as aliphatic or aromatic sulfonates or corresponding acids.
One serious disadvantage is that the leveling action of the known brightening agents is poor, resulting in only moderately bright nickel deposits. Another disadvantage is the brittleness of the nickel deposits obtained with these brighteners.
In order to overcome the aforementioned disadvantages it is common to include additional components in the plating bath e.g. saccharin for the purpose of promoting the deposition of more ductile nickel coating. Although saccharin, which is a sulfo-oxygenated compound, is sometimes referred to as a brightener, it does not by itself yield bright nickel plating but acts primarily as a stress reducer. A leveling agent is also included to promote the formation of a smoother surface of the plated out nickel. One such leveling agent of particular interest is the one disclosed in French Patent No. 2,160,737. The agent is a quaternary compound obtained by reacting an acetylenic mono-ester of a halogenated saturated aliphatic acid with a heterocyclic compound having a tertiary nitrogen. The resulting acetylenic quaternary compound is required to be used in combination with an organic sulpho-oxygenated compound. When these compounds are added to a plating bath, enhanced brilliance and leveling of the nickel deposits were said to be obtained. In further studies, however, which were carried out for the purpose of evaluating the aforementioned compounds of the French patent as leveling agents, it was found that although leveling was improved to a certain degree, their performance could only be rated as average.
It is therefore a general object of the present invention to provide a novel-brightener-leveling agent having improved properties over those of the prior art compositions.